(1) Field of the Invention
This invention relates to a process for the synthesis of greases permitting a good control of their mechanical behaviour.
(2) Description of the Related Art
Greases are colloidal systems made up of a three- o dimensional network of thickening molecules in an oil.
The thickeners employed to form this network may be, for example, metal soaps, by themselves or mixed with polymers.
The oil belongs to the class of lubricating oils. This oil is trapped and kept within the three-dimensional network of the thickener by a combination of capilliary, adsorption and steric interaction forces.
Greases are widely employed for lubricating rotating mechanical components, in fields as diverse as domestic appliances, motor vehicles or aviation. They have the advantage of a great ease of application and of a reduced maintenance.
The properties of greases can be improved by the use of additives. It is thus possible to improve the resistance to oxidation, to wear and to corrosion by the addition of amine salts, of metal sulphates, of naphthenates, of esters and of nonionic surfactants to the greases.
The extreme-pressure properties can be improved by the addition of graphite, molybdenum disulphide, zinc oxide or talc.
It is also known to modify the mechanical properties of greases by varying the proportion of metal soap and the heat treatment during their process of manufacture.
The conditions of use of greases frequently call for contradictory properties. Thus, for a given consistency and mechanical working strength it is sometimes advantageous to have increased adhesion and/or fluidity properties. Currently known means do not allow this problem to be solved.
We have now found a process which, on the one hand, permits a good control of the mechanical behaviour of greases and, on the other hand, makes it possible to modify the contradictory mechanical properties in a continuous way.